Valves are used in a wide variety of applications for controlling the flow of solid, liquid, and gaseous materials. Such control may be simply on or off or the rate of flow of the material may be controlled by the valve. In many cases, it is desirable to have a valve that is operated by a motor or actuator. Such cases include those in which the valve is automatically operated by a controller.
Many such valves require linear motion to effect the opening and closing of the valve and are controlled by linear actuators. Known conventional linear actuators suffer from various problems, among which are:                1. Alignment of the valve stem or plunger is difficult to maintain because of tolerance stack-up of the many components of the actuator.        2. A discrete valve and actuator combination is often difficult to assemble.        3. Discrete components are often redundant and, therefore, the resulting assembly is more expensive than necessary.        
The root cause of most problems with linear valve actuators is that they are of separate construction from the valves that they operate.
Accordingly, it is a principal object of the present invention to provide a linear valve actuator that is simple.
It is a further object of the invention to provide such a linear valve actuator that has low parts count.
It is an additional object of the invention to provide such a linear valve actuator that is economical.
It is another object of the invention to provide such a linear valve actuator that is easily assembled with a linear valve.
Yet a further object of the invention is to provide such a linear valve actuator that permits accurate alignment of the valve stem or plunger with the components of the linear valve actuator.
Other objects of the present invention, as well as particular features, elements, and advantages thereof, will be elucidated in, or be apparent from, the following description and the accompanying drawing figures.